Rotary loop forming device for sewing machines



June 3, 1969 YOSHIHIKO NAKAJIMA L ROTARY LOOP FORMING DEVICE FOR SEWING MACHINES Filed March 22, 1966 Sheet N INVENTORS June 3, 1969 YOSHIHIKO NAKAJIMA AL ROTARY LOOP FORMING DEVICE FOR SEWING MACHINES Filed March 22, 1966 Sheet June 3, 1969 YOSHIHIKO NAKAJIMA ET AL 3,447,499

ROTARY LOOP FORMING DEVICE FOR SEWING MACHINES Sheet Filed March 22, 1966 I NVENTORS V0 54mm; Ala (r .June 3, 1969 YOSHIHIKO NAKAJIMA ET AL 3,447,499

ROTARY LOOP FORMING DEVICE FOR SEWING MACHINES Sheet Filed March 22, 1966 June 3, 1969 YOSHIHIKO NAKAJIMA ETAL 3,447,499

RQTARY LOOP FORMING DEVICE FOR SEWING MACHINES Sheet Filed March 22, 1966 INVENTORS osidLA LL A2117, 4

June 3, 1969 YOSHIHIKO NAKAJIMA ET AL 3,447,499

ROTARY LOOP FORMING DEVICE FOR SEWING MACHINES Sheet Filed March 22, 1966 June 3, 1969 YOSHIHIKO NAKAJIMA ET AL 3,447,499

ROTARY LOOP FORMING DEVICE FOR SEWING MACHINES Sheet 7 Of8 Filed March 22, 1966 June 3, 1969 yos o NAKAJIMA ET AL 3,447,499

ROTARY LOOP FORMING DEVICE FOR SEWING MACHINES Filed March 22, 1966 Sheet 6 of 8 BY 14 L, z Ing (4' H11 a United States Patent US. Cl. 112-228 14 Claims ABSTRACT OF THE DISCLOSURE A rotary looper or hook member is fully supported in a stationary race and driven by a drive shaft which is connected with the rotary hook member by coupling means which permit the passage of a newly formed thread loop between the drive shaft and the hook member.

The present invention relates to a rotary loop forming device, and more particularly to a sewing machine with a rotary loop forming device in which a rotary hook member holds a bobbin with a thread, and loops the upper thread supplied by the needle of the sewing machine over the lower bobbin thread in such a manner that a switch is formed of the two threads.

Conventional household sewing machines employ oscillating shuttles which turn 180 only, so that the inertia of the oscillating shuttle body is not utilized and has to be overcome by the drive means so that the action is noisy and jerky, preventing operation of the machine at high speed. Therefore, sewing machines for industrial use are preferably provided with rotary hook members enveloping an inner shuttle body. Known rotary hook loop formers are rather complicated, and if any repair or adjustment has to be carried out, special tools are required for taking out the inner shuttle body and for fitting it again into the shuttle assembly. Such operations cannot be properly performed by unskilled persons using sewing machines in their homes, since the accurate adjustment of the shuttle is too difiicult and requires great skill. Therefore, rotary hook loop formers are not used for household sewing machines, and oscillating shuttles are preferred for this purpose, although they have disadvantages as compared with rotary loop formers.

It is one object of the invention to overcome the disadvantages of oscillating shuttles by providing a rotary loop former of simple construction, which can be easily adjusted and used, but operates at high speed.

Another object of the invention is to provide a rotary loop forming device for a sewing machine in which a rotary hook member holds the bobbin and can be detached together with the bobbin without any tools so that the bobbin can be inserted or removed machine.

Another object of the invention is to mount a rotary bobbin-supporting hook member in a stationary outer race in such a manner that the hook member can be easily detached from the race.

Another object of the invention is to mount a bobbinsupporting rotary hook member in such a manner that it can be rotated by drive means, but can be nevertheless removed from the sewing machine for the insertion or removal of a bobbin.

Another object of the invention is to provide a rotary loop forming device in which a bobbin is mounted in a detachable manner in a similar manner. as in conventional oscillating shuttle sewing machines.

Another object of the invention is to provide a rotary outside of the sewing loop forming device which does not require any special tools for the correction of minor disturbances.

Rotary loop forming devices for sewing machines require a continuous-driving connection between rotary drive means and the rotary loop forming member so that after a thread loop supplied by the needle of the sewing machine is caught by the rotary hook, a portion of the thread loop sliding in tensioned condition over the outer surface of the rotary hook member could not pass the region where the drive means is connected with the rotary hook member so that the needle could not pull up the thread. Consequently, it is necessary to provide means permitting the thread to pass between the drive means and the rotary hook member, and therefore it is not possible to rotate the shuttle in standard sewing machine constructions where the shuttle is removable.

Therefore, the present invention provides coupling means between the drive means and rotary loop forming member which are of such a construction as to permit the passage of portions of the loop formed by the hook of the loop forming member or looper.

One embodiment of the invention comprises stationary race means; a loop forming hook member fully supported by the race means for rotation and having a hook for catching a thread supplied by the needle and for drawing a thread loop about the hook member during each revolution of the same; rotary drive means, prefer-ably including a drive shaft which does not support the hook mem her; and a plurality of coupling means, preferably two coupling means for connecting the drive means with the hook member for rotating the latter.

In accordance with the present invention, the coupling means are cyclically and successively moved by the rotary drive means between engaged and disengaged positions. Each coupling means is the disengaged position forms a gap for the passage of a portion of the thread loop. The gap is formed between a first coupling member on the hook member and a second coupling member on the drive means. One portion of the thread loop passes between the first and second coupling members when the respective coupling means is disengaged and the coupling members form a gap, whereupon the rotation is continued until a second loop portion passes through the gap between the first and second coupling members of the other coupling means in the disengaged position. Thereby, the thread loop is not held by the coupling means between the drive means and the rotary hook member, but can be withdrawn from the hook member after one revolution of the same by retraction of the needle. During this operation, the thread loop forms a stitch with the thread of the bobbin held by the hook member in the usual manner.

In the preferred embodiment of the invention, the stationary race means include an outer fixed race member, a retainer cap inserted into the race member, and locking means for locking the retainer cap in a position preventing axial movement of the rotary hook member out of the race member.

While this structure permits the detachment of the bobbin holding hook member by a manual operation, rotation of the'hook member is nevertheless possible due to the above explained construction of the coupling means which are alternately in engaged positions for driving the rotary hook member and in disengaged positions for permitting passage of a portion of the thread loop.

The alternate engagement and disengagement of two coupling means is accomplished by moving the first and second coupling members of each coupling means relative to each other.

In one embodiment of the invention, the rotary hook member has a first axis of rotation, and the rotary drive means has a second axis of rotation parallel to the first axis, but eccentric to the same. Therefore, a relative movement takes place between the first coupling members on the rotary hook member and the second coupling members on the drive shaft. The first and second axes are located in a common plane slanted to the vertical plane in which the needle moves, and the spacing between the two axes is selected so that the first and second coupling members of each coupling means form gaps at the moment at which the thread loop approaches the same so that the thread loop can pass between the spaced first and second coupling members.

In another embodiment of the invention, the axis of the rotary hook member intersects the axis of the rotary drive means at an angle. During rotation of the drive means, the coupling members on the drive shaft move in substantially axial direction between the engaged position and the disengaged position, and assume the dis engaged position forming a gap at the moment in which a thread portion of the thread loop approaches the respective coupling means so that the same can be passed by the thread 100p, while the driving connection between the drive shaft and the rotary hook member is maintained by the other coupling means whose first and second coupling members are in the engaged position.

Due to the fact that the rotary hook member is rotated, the operation produces very little noise, and high rotary speeds are possible. Due to the fact that the drive shaft is parallel and eccentric, or slanted to the axis of the rotary hook member, the coupling members come into contact at a relatively slow speed so that very little noise is created.

In the embodiment of the invention in which the axes of the drive shaft and of the rotary hook member are parallel so that the drive shaft and the hook member are eccentric, the actual rotary speed of the hook at a moment in which the thread is caught can be determined by suitably selecting the distance between the parallel axes. In this manner the thread loop is caught by the hook of the rotary hook member while the hook moves at a higher speed than at other portions of its circular path. Due to the high speed of the hook in the catch position, the thread supplied by the needle is reliably and positively caught. As a result, the rotary hook member of the invention permits operation of the sewing machine at a very high speed while the thread is reliably caught whereby perfect stitching is obtained.

The rotary loop forming device of the invention is particularly advantageously used in zig-zag sewing machines. The catching of the thread loop is more difiicult in machines of this type because of the lateral movement of the needle which supplies the thread to the loop forming hook. Due to the high speed of the rotary hook according to the invention, the thread is positively caught even if the needle laterally oscillates at a large amplitude.

In the second embodiment of the invention in which the axis of rotation of the rotary hook member and the axis of rotation of the drive shaft intersect each other, the coupling members on the drive shaft and hook member move toward and away from each other and open a wide gap in the disengaged position through which portions of the thread loop can easily pass. The coupling members on the drive shaft are completely retracted from the coupling members on the rotary hook member so that a very wide gap is formed by one pair of coupling members for the passage of a thread loop, while another pair of coupling membersare engaged to effect continuous driving of the rotary hook member from the drive shaft.

In the first embodiment of the invention two diametrically arranged coupling members are mounted on the drive shaft, and project into corresponding cutouts in an annular wall of the rotary-hook member. In the engaged position, a coupling member on the drive shaft abuts a radial edge of the wall bounding the respective cutout, and in the disengaged position, the respective coupling member is located in the cutout spaced from the edges of the same forming a gap through which the thread loop can pass. In the embodiment in which the axes of the drive shaft and of the rotary hook member are parallel, the coupling member on the drive shaft may remain in the cutout in the disengaged position, but in the embodiment in which the axes intersect at an angle, the coupling members of the drive shaft are completely retracted in substantially axial direction from the cutouts in the wall of the rotary hook member.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIGS. 1 to 6 illustrate a first embodiment of the invention; and FIGS. 7 to '12 illustrate a second embodiment of the invention.

FIG. 1 is a fragmentary front view, partially in section, illustrating a sewing machine provided with a loop forming device according to the invention;

FIG. 2 is a fragmentary end view of the sewing machine, partially shown in vertical section;

FIG. 3 is a front view of the loop forming device;

FIG. 4 is a sectional view taken on line 1"VIV in FIG. 3;

FIG. 5 is an exploded perspective front view of the loop forming device;

FIG. 5a is a perspective rear view of the hook member of the loop forming device;

FIG. 6 is a series of fragmentary front views (A) to (I) illustrating a sequence of operational positions of the hook member during one revolution for forming a thread loop;

FIG. 7 is a fragmentary front view, partially in section, illustrating a sewing machine provided with a loop forming device according to a second embodiment of the invention;

FIG. 8 is a fragmentary end view of the sewing machine with the loop forming device of FIG. 7, partially shown in section;

FIG. 9 is a front view of the loop forming device;

FIG. 10 is a sectional view taken on line XX in FIG. 9;

FIG. 11 is an exploded perspective front view of the loop forming device;

Referring now to the drawings, and more particularly to FIGS. 1 to 6, a sewing machine has a casing 26 with an oscillating thread guiding arm 30 and thread tensioning means 31. A needle bar assembly 27 reciprocates a needle 28 through a slot in a pressor foot 29 so that a fabric on the top of table 25 is pierced by the needle 28 carrying the upper thread. A drive shaft, not shown, rotates a large bevel gear 24 which meshes with a bevel pinion 23 on a drive shaft 17 supported in walls 20 of the gear box 25. As best seen in FIG. 4, a bearing sleeve .14 supports a shaft portion of greater diameter for rotation and is secured by a set screw 34 and a ring 22 held on the shaft 17 by another set screw 36. Bevel gear 23 is secured to shaft 17 by screw 3-7, and the hub of bevel gear 23 engages the inner surface of a wall of gear box 21 to prevent axial movement of shaft 17 whose end is supported in a bearing in the same wall. I

As best seen in FIGS. 4 :and 5, drive shaft 17 carries a coupling part 18 which includes a pair of coupling members 19 and 19 which have the same circumferential thickness as best seen in FIG. 6, but different outlines as best seen in FIGS. 4 and 5.

Coupling members 19 and 19 are respectively located in cutouts 5a and 5a in the rear wall of a hook member 1. As best seen in FIG. 5a and 4,- the rear wall of the hook member 1 includes a flat circular center portion and a substantially 'frustoconical or slightly curved annular slanted portion 4', and cutouts 5a and 5a extend in both wall portions 4 and 4' so that the edges 5 and 5 of the dished rear wall 4, 4' which bound cutouts 5a, 5a are angular and have radially outer portions which are farther spaced from the corresponding coupling portions 19 and 19' than the radially inner portions which are located in the central wall portion 4, as best seen in FIG. 4. Hook member 1 further includes an annular dished front wall 3 with a large central opening permitting insertion of a bobbin, not shown, which is attached to a bobbin carrier pin 9. A hook portion 2 extends about the periphery of hook member 1 between front wall 3 and rear wall portion 4' and has one end 6 formed as a hook, and a blunt end 7 separated from hook 6 by a cutout 33. Between hook portion 2 and front wall portion 3, a substantially semi-circular slot 8 is provided for the passage of the sewing needle so that hook member 1 can rotate substantially half a revolution while the needle 28 is in the lower position located in slot 8.

Stationary race means are secured to the underside of table 25, as best seen in FIGS. 1 and 2, and include an outer race member '10 having locking arms 16 mounted on pivot screws 38, and a retainer cap 15, as best seen in FIG. 5.

Outer race member 10 has an annular bearing surface including a cylindrical portion 12. and an annular portion 12" located in a radial plane and connected with a dished rear wall 13 which has large cutouts 13a for coupling members 19 and 19 and includes a yoke portion 13 connected with a hub 14 by means of which the outer race member 10 is mounted on the table25 of the sewing machine while permitting passage of drive shaft 17 into the gear box 21. At the open front end of race member 10, a cylindrical wall 11 has brackets supporting pivot screws 38 for the locking arms 16. Wall 11 has an inner cylindrical surface 11' connected with surface 12 by a surface 12 which is located in a radial plane.

The top of outer race member 10 is cut off along a curved surface 10a.

The retainer cap 15 has a front wall 15a, a cylindrical surface 12b, and a rear surface 15c. When the retainer cap is inserted into the outer race member, surface 1522 matches surface 11', and surface 15c abuts surface 12. A cutout spring member 15d is located on the surface 10a of the outer race member and closes the interior of the same except for the cutout 15e which permits the passage of needle 28, and which has suficient axial width to permit an oscillating motion of the needle during a zigzag stitch.

Surface 150 has an inner edge of smaller diameter than surface 12, so that surfaces 15c, 12', and 12" form a circular race or guide way for the hook portion 2 of hook member 1, with surface 2a of hook member 1 sliding on surface 12', as best seen in FIG. 4. Retainer cap 15 is held in place by locking arms 16 which are turned to the locking position shown in FIGS. 1 and 3 abutting front wall 15a of retainer cap 15. Pins 15c arrest the locking arms. in the locking position.

When rotary hook member 1 is mounted within the race means 10, 15, it is non-movable in axial direction, but rotatable about an axis defined by the center of surface 12'. This axis of rotation of hook member 1 is parallel to the axis of rotation of drive shaft 17, and consequently the axis of rotation 0 of rotary hook member 1 is eccentric to the axis of rotation 0 of shaft 17, as best seen in FIG. 6 A. The axis 0 of rotary hook member 1 is spaced a distance 6 in horizontal direction and a distance 8' in vertical direction from the axis 0 of shaft 17.

During a sewing operation, the rotary hook member is enclosed and locked in the race means 10, 15. in t e position of FIG. 4 in which coupling members 19 and 19 of drive shaft 17 are located in cutouts 5a, 5a in the rear wall 4, 4' of hook member 1. Since the axes of hook member 1 and drive shaft 17 are eccentric, a relative movement takes place between coupling members 19, 19' and the edges 5, 5 which constitute coupling members on book member 1 cooperating with coupling members 19, 19. Coupling member or coupling portion 5 cooperates with coupling portion 19, and forms with the same a first coupling means, and coupling member or portion 5' cooperates with coupling portion 19' and forms with the same a second coupling means so that drive shaft 17 is connected with the rotary hook member 1 by two coupling means. The two coupling means are alternately and cyclically in engaged and disengaged positions during each revolution, which is caused by the eccentricity of the axes of shaft 17 and hook member 1, as will now be explained with reference to FIG. 6.

In the position A, hook 6 has just caught a thread N supplied by needle 28. Coupling portion 5 is engaged by coupling portion 19 so that coupling means 5, 19' is engaged and shaft 17 drives hook member 1 clockwise. Due to the eccentricity of axes 0, 0', coupling member 19 is spaced from coupling portion 5, and coupling means 5, 19 is in a disengaged position and does not transmit the driving torque to hook member 1.

Shaft 17 turns hook member 1 by coupling means 19', 5' first to the position B, and then to the position C, while a thread loop of increasing size is formed by hook 6. The lateral portions of thread loop R are respectively located on opposite sides of hook member 1. When the imaginary plane in which coupling means 5, 19, 5', 19' are located passes the plane in which axes 0, 0 are located, coupling member 19 moves to a position engaging coupling portion 5, while coupling member 19 is spaced from coupling portion 5' in the position D. While hook member 1 increases the size of the loop, the position E is reached in which the portion R of thread loop R on the rear wall 4, 4' of hook member 1 passes the region of coupling means 5', 19' which are in a disengaged position forming a gap through which thread portion R can pass during further rotary movement of hook member 1.

The rotation is continued first to position F in which the thread loop is slackened and then to a position G in which the thread loop is reduced in size due to the up wards movement of needle 28.

When the operative coupling means 5, 19 moves through the slanted plane defined by axes 0, 0, coupling means 5, 19 is disengaged, and coupling means 5', 19 is engaged in the position H, while the thread loop has been further reduced by the needle so that the thread portion R" which is released by hook 6 in this position, slides over the periphery of hook member 1 and forms a small loop about coupling member 19. Since coupling member 19 is disengaged and forms a gap with coupling member 5, the loop can be pulled out in the position I, which is facilitated by the shape and curvature of surface 19a of coupling member 19, as best seen in FIG. 4. Since in the position E, thread portion R slides in radially inward direction over coupling member 19', the latter has a corresponding slanted outer guide surface 19'a.

As 'is well known to those skilled in the art, the retracted loop R will form a stitch with the lower thread of the bobbin hook member I mounted on bobbin holding pin 9. It will be understood that due to the eccentricity of the axes 0, 0, book member 1 is alternately accelerated by the driving coupling members 19, and 19' which rotate at a uniform rotary speed. When one of the driving coupling members 19, 19 drives hook member 1, the other driving coupling member forms a gap with the respective coupling portion or coupling member 5, 5' of the hook member and during each revolution, the tWo coupling means are alternately engaged and disengaged so that passage of the thread loop through the coupling means is possible.

In order to place coupling means 5, 19' in the disengaged position E at the moment in which thread portion R passes through the region of coupling means 5, 19', the plane in which the eccentric axes 0, are located forms an angle with horizontal and vertical planes and trails in direction of rotation the vertical plane in which hook 6 is located, while the imaginary plane in which coupling means 5, 19, 19 are diametrically arranged, leads hook 6 a small acute angle in the direction of rotation.

In the position I, coupling member 19 is not only circumferentially spaced from coupling portion 5 and from the opposite edge of cutout 5a, but is located radially outward in relation to cutout 5a. Since the radially outer portion of cutout 5a is located in the slanted, substantially frustoconical wall portion 4' of hook member 1, the outer end of coupling portion 19 is also axially spaced from cutout 5a and coupling portion 5 so that the passage of the thread loop is facilitated. The radial movement of coupling portions 19, 19' in cutouts 5a, 5a in addition to the circumferential movement is obtained by suitably selecting the distance between axes 0, 0 and the slant of the plane in which the axes are located. Axis 0 of drive shaft 17 has to be located above and trailing in the direction of rotation with respect to axis 0 of the rotary hook member. If the position of the axes 0, 0' is so chosen, book 6 will move at maxi-mum speed when catching thread N in the position A. At the moment in which the imaginary plane in which coupling means 5, 19, 5', 19 passes through the plane in which axes 0, 0' are located, rotary hook member 1 moves at its minimum rotary speed while both coupling means are momentarily disengaged and hook member 1 continues its rotation by inertia. This position is assumed between position C, D, and positions G, H.

A second embodiment of the invention will now be described with reference to FIGS. 7 to 12. It will be appreciated that the outer race member 10, the retainmg cap 15, rotary hook member 101, and drive shaft 117 with driving coupling projections 119 and 119' correspond substantially to the construction of FIGS. 1 to 6 and consequently like parts are indicated by like reference numerals while modified parts are designated by reference numerals having the prefix 1.

As shown in FIG. 8 a drive shaft 117 is driven by gears 24, 23, and as best seen in FIG. 11, drive shaft 117 has a pair of diametrically arranged driving coupling portions 119, 119' which are respectively located in cutouts 105a, 105a bounded by coupling portions 105, 105 in a rotary hook member 101 which is otherwise constructed as described with reference to hook member 1. Hook member 1 is mounted for rotation in the race means 10, 15, when retainer cap 15 is locked by locking means 16.

In contrast to the embodiment of FIGS. 1 to 6, the

- cutouts 105a, 105' are narrow and have a circumferential width substantially corresponding to the thickness of coupling members 119, 119.

As in the embodiment of FIGS. 1 to 6, the diametrically arranged coupling means 119, 105 and 119', 105' are alternately and cyclically placed in engaged and disengaged positions due to the relative position between the axis of drive shaft 117 and the axis of rotation of rotary hook member 101 which is defined by the center of surface 12 of outer race member 10. However, in contrast to the embodiment of FIGS. 1 to 6, the two axes are not parallel and eccentric but the axis of drive shaft 117 intersects the axis of rotation of rotary hook member 101 at an obtuse angle so that the two axes are located in the same plane.

The angle between the two axes is best seen in FIG. 12E in which the plane of the two axes coincides with a vertical plane. The axis of book member 101 represented by pin 9 is horizontal, whereas the axis of drive shaft 117 is inclined to the horizontal. As is clearly apparent from FIG. 12E, coupling projection 119 is located outside of cutout a due to the slant of shaft 117, while coupling projection 119 is located in the cutout 105a and consequently in coupling engagement with coupling portion 105 constituted by the radial edges of rear wall 4, 4' bounding cutout 105a.

The formation of a thread loop by the rotary hook member 101 will now be described with reference to FIG. 12. In the position A, hook 6 is located in a vertical plane and has just caught a thread N supplied by needle 28, not shown. Coupling means 105, 119 lead hook 6 in the clockwise direction of rotation of drive shaft 117 a small acute angle, and due to the inclination of drive shaft 117, coupling member 119 is located outside of cutout 105a so that coupling means 105, 119 is disengaged. Coupling means 119, 105 is engaged since coupling member 119' is located in cutout 105a. Consequently, hook member 101 is rotated by drive shaft 117 through coupling 105, 119.

In the position B, B, both coupling means are engaged with coupling members 119, 119 located in cutouts 105a, 105a, and the loop R is increased in size. In an intermediate position, not shown, the axes of hook member 101 and of drive shaft 117 are located in a horizontal plane. Coupling member 119 has been pushed into cutout 105a and coupling member 119' has been slightly retracted from cutout 105a.

In the position C, C, thread loop R has been drawn to its maximum size and portions thereof are located on opposite sides of hook member 101. Thread portion R passes the region of coupling means 119', 105' and since coupling member 119' is not located in cutout 105', thread portion R passes through the gap between coupling members 105 and 119', while hook member 101 continues its rotation.

In the position D, D, the size of the thread loop has been reduced by upward movement of the needle, not shown, and hook 6 is in a position releasing the thread loop R. Loop portion R approaches coupling means 119, 105 which is still engaged since coupling member 119 is partly located in cutout 105a.

In the position E, E coupling members 119 and 119' are located in a vertical plane. Since coupling members 119, 119' are located in the plane in which the axis of hook member 101 and the axis of drive shaft 117 intersect, coupling portion 119 is retracted as far as possible from cutout 105a, and coupling portion 119' is fully inserted into cutout 105a. While coupling means 119', 105' is engaged so that hook member 101 is rotated by drive shaft 117, the gap between coupling members 119, 105 of the other coupling means permits the thread loop to be further reduced and to slip through the gap so that the thread loop is fully retracted by the needle to form a stitch with the lower thread supplied by a bobbin, not shown, mounted on pin 9 in hook member 101.

The inner slanted surface 119a facilitates the movement of the thread through the gap and the corresponding function is performed by the slanted outer surface 119a in the position C, C.

Further turning of hook member 101 by drive shaft 117 places hook 6 again in a vertical plane to catch the thread as shown in position A of FIG. 12.

In the embodiment of FIGS. 7 to 12, one or both coupling means 119, 105 and 119', 105 are engaged at any time so that a continuous driving connection is established between drive shaft 117 and hook member 101, resulting in a smooth and noiseless operation. Each engaged coupling member 119, or 119 while being withdrawn from the engaged position, guides the respective other coupling member 119', 119 into the corresponding cutouts in the rear wall of hook member 101.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of rotary loop formers for sewing machines differing above.

While the invention has been illustrated and described as embodied in a rotary loop forming device in which two diametrically arranged coupling means are alternately engaged and disengaged for connecting a drive shaft with a rotary hook member, and for permitting passage of a thread loop, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge readily adapt it for variious applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention, and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A rotary loop forming device for a sewing machine, comprising, in combinatio stationary annular race means; a hook member supported in said race means for rotation in one direction about a first axis and having means for supporting a bobbin, a hook for catching a thread and for drawing a thread loop about said hook member during a revolution of the same, said hook member having a wall formed with two diametrically disposed cutouts bounded on the side leading in said direction of rotation by wall portions constituting first coupling members; rotary drive means rotating in said direction of rotation about a second axis parallel to and spaced from said first axis; two diametrically disposed second coupling members carried by said drive means and rotated by the same, said second coupling members respectively cooperating with said cutouts and first coupling members to form two coupling means with the same, said first and second axes having such a relative position that said second coupling members are alternately moved between a position abutting the respective first coupling member, and a position spaced from the same so that said coupling means are alternately in engaged and disengaged positions, each coupling means in said disengaged position forming a gap between the respective first and second coupling members for the passage of a portion of said thread loop while the other coupling means is in said engaged position so that said drive means rotates said rotary hook member continuously during a revolution during which said thread loop is withdrawn from said hook member first through one and then through the other coupling means in said disengaged position.

2. A rotary loop forming device according to claim 1, wherein said cutouts are radial slots; wherein said hook member wall is curved in radial direction so that said wall portions are curved; and wherein said second coupling members have curved portions moving in said slots and forming guide faces for the thread.

3. A rotary loop forming device according to claim 1, wherein said race means include manually operable retaining means for said hook member; and wherein said hook member is removable from said race means in axial direction upon release of said retaining means.

4. A loop forming device according to claim 1, wherein said hook catches said thread when located in a vertical plane; wherein one portion of said thread loop passes between said first and second coupling members of one of said coupling means in said disengaged position when said hook member has turned an angle of substantially 180 so that said hook is again located in said vertical plane, and wherein another portion of said thread loop passes between said first and second coupling members of the other coupling means when said first and second coupling members are substantially located in said verfrom the types described tical plane so that said thread loop is withdrawn from said hook member shortly before said hook catches a thread.

5. A rotary loop forming device according to claim 1, and wherein said first and second coupling members have substantially radial engaging faces so as to be movable relative to each other whereby manual detachment of said rotary hook member with said first coupling members in substantially axial direction can be carried out by a manual operation so that a bobbin can be placed in or removed from said rotary hook member when the same is located outside of said race means.

6. A rotary loop forming device for a sewing machine comprising, in combination, stationary race means; a hook member mounted in said race means for rotation about a first axis, and having a hook for catching a thread and for drawing a thread loop about said hook member during each revolution of the same; rotary drive means including a drive shaft having a second axis of rotation, said first and second axes being parallel so that said second axis is eccentric to said first axis; and a plurality of coupling means for connecting said drive shaft with said hook member for rotating the latter, each of said coupling means including a first coupling member on said hook member and a second coupling member on said drive shaft; said first and second axes being disposed for cycli cally and successively moving said first and second coupling members between engaged and disengaged positions, each coupling means in said disengaged position forming a gap between said first and second coupling members for the passage of a portion of said thread loop while another coupling means is in said engaged position, said first and second coupling members of each coupling means being circumferentially spaced in said disengaged position and abutting each other in said engaged position so that said thread loop can be withdrawn from said hook member after the same has been turned one revolution by said drive means.

7. A rotary loop forming device according to claim 6, wherein each of said coupling members has a radial portion and a portion slanted relative to said first axis and located radially outward of said first portion; and wherein due to the eccentric position of said second axis in relation to said first axis said second coupling members move radially outward during movement to said disengaged position so as to be located in the region of said slanted coupling portions whereby said first and second coupling members are separated in said disengaged position also in axial direction.

8. A rotary loop forming "device according to claim 6, wherein said first and second axes are horizontal and located in a plane angularly spaced from a horizontal plane an angle smaller than in the direction of rotation.

9. A rotary loop forming device according to claim 6, wherein said first and second axes are horizontal and wherein said second axis is located above a horizontal plane passing through said first axis.

10. A rotary loop forming device according to claim 9, wherein said first and second axes are located in a plane angularly spaced from said horizontal plane an angle smaller than 90 in the direction of rotation of said hook member.

11. A rotary loop forming device according to claim 10, wherein said plurality of coupling means are two coupling means, wherein said first coupling members are diametrically disposed; and wherein said second coupling members are diametrically disposed.

12. A rotary loop forming device for a sewing machine, comprising in combination, stationary race means; a hook member mounted in said race means for rotation about a first axis, and having a hook for catching a thread and for drawing a thread loop about said hook member during each revolution of the same; rotary drive means having a second axis of rotation parallel to said first axis so that said second axis is eccentric to said first axis; and a plurality of coupling means for connecting said drive means with said hook member for-rotating the latter, said coupling means being cyclically moved by said rotary drive means between engaged and disengaged positions, each coupling'means in said disengaged positions forming a gap for the passage of a portion of said thread loop while another coupling means is in said engaged position so that said thread loop can pass over and be withdrawn from said hook member through said coupling means in said disengaged position.

13. A rotary loop forming device according to claim 12, wherein said race means include manually operable retaining means for said hook member; and wherein said hook member is manually removable from said race means upon release of said retaining means.

14. A rotary loop forming device according to claim 12, wherein said race means include an outerstationary race member, a retaining cap positioned in said outer race member for retaining said hook member, and locking means on said outer race member for locking said retaining cap; and wherein said hook member is mounted in said outer race member for axial movement so that upon References Cited UNITED STATES PATENTS 2,219,470 10/ 1940 Carlson 1124-232 558,662 4/1896 Richards 112-189 607,080 7/1898 Richards 112-189 1,173,973 2/1916 Illig 112-189 2,148,385 2/1939 Waterman 112228 X 2,761,402; 9/ 1956 Johnson 11222J8 X 2,941,488 6/ 1960 Attwood 112228 2,988,030 6/ 1961 Schenkengel 112-228 I IERB'ERT F. ROSS, Primary Examiner.

- us. 01. X.R. 112 1s1, 231 

